Coarse density measurement
Cost: 1 credit.
Return to chemistryHS03 · CUMULATIVE VIRTUAL INVESTIGATION
Identify an unknown and defend a separation
Choose measurements, compare candidate explanations and preserve a report for review.
Useful preparation: density and measurement bounds, solubility and mixtures, and separation and recovery. All lessons remain directly accessible.
Your investigation contract
Identify fictional sample U-01 from the three candidates below. Then plan how to separate a mixture of 10 g of that sample and 25 g of soluble solid A. A has capacity 20 g per 100 g water at the same stipulated conditions. Assume the candidate table is exhaustive for the identification task; discuss what changes if that assumption is false.
Candidate values and observations are original programmed teaching data, not measured material properties. Tests operate on representative separate aliquots of the same uniform sample; they do not consume the mixture used in your separation plan. The case is fixed and publicly inspectable in the browser. This is an investigation exercise, not a secure examination.
| Candidate | Density at matched conditions | Water dissolution at equilibrium |
|---|---|---|
| M1 | 1.20 g/mL | 20 g per 100 g water |
| M2 | 2.70 g/mL | Insoluble in this model |
| M3 | 2.80 g/mL | 20 g per 100 g water |
Compare the possible outcomes and cost of a test before requesting it. Cost credits are teaching constraints, not money, elapsed time or measured laboratory expenses. You may submit an inconclusive claim if your evidence does not distinguish the candidates.
Choose evidence within the budget
0/3 credits spent; 3 remaining. Recorded tests cannot be reset or refunded.
This pending text is not saved until you request a test. Its recorded copy stays with that test; later report drafts may revise your interpretation.
Equilibrated dissolution test
Cost: 2 credits.
Finer density measurement
Cost: 3 credits.
Draft the scientific argument
Use measured intervals as intervals, distinguish compatibility from proof, and state whether your identification depends on the candidate list. For the separation plan, include solvent amount, each fraction, recovery and a check for contamination. Cite the observations by test name.
Each field allows 2,400 characters. Saving requires at least one recorded test and nonempty text in every field. These checks do not assess correctness, purity, practical technique or writing quality.
The first report cannot be replaced. After critique, edit the draft and save one retained revision below. Legacy submissions remain the first report. Tests and known observations are never refunded.
Review with evidence and revision
- Does the test rationale compare candidate outcomes and respect the budget?
- Do the claim and calculations follow from the actual observations, including interval overlap?
- Does the alternative explanation identify a plausible failure of a stated assumption and a discriminating check?
- Does the separation plan track every component and distinguish recovery from purity?
- Are simulated results, real practical competence and remaining uncertainty distinguished?
A reviewer should cite a passage or calculation for each judgment and request a targeted revision. A correct candidate label alone is insufficient. For independent transfer, use a fresh problem with different properties or a new dataset; repeating this public case does not create an unseen assessment.
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